In recent years, an AC motor is applied for power in the fields of industrial machines and home appliances and transportation fields of an automobile, an electric motor vehicle, and the like. To drive the AC motor, a DC power supply or an AC power supply is necessary. In general, a power converting apparatus for motor driving for which the DC power supply is used as an input power supply has a configuration in which the power converting apparatus receives input of a DC voltage supplied from the DC power supply, generates an AC voltage having an arbitrary frequency with an inverter circuit, and drives the AC motor. In general, a power converting apparatus for which the AC power supply is used as an input power supply has a configuration in which the power converting apparatus includes a converter circuit on an input side, once converts an AC voltage received by the converter circuit into a DC voltage, and supplies this DC voltage to the inverter circuit to drive the AC motor.
The configuration and the like of the power converting apparatus for motor driving are explained with reference to a power converting apparatus for motor driving used for an AC electric railway as an example. A stringing voltage as an AC power supply is a single-phase AC voltage of 20 kilovolts to 25 kilovolts. This single-phase AC voltage is stepped down to about 1 kilovolt to 2 kilovolts by a transformer and then input to the converter circuit of the power converting apparatus for motor driving. The converter circuit receives the input of the single-phase AC voltage of 1 kilovolt to 2 kilovolts, converts the single-phase AC voltage into a DC voltage of about 1500 volts to 3000 volts, and outputs the DC voltage to the inverter circuit.
It is known that the DC voltage as the output of the converter circuit includes pulsation of a frequency component twice as large as an AC power supply frequency (hereinafter referred to as “power supply 2f component”). When the frequency of the AC motor is near this power supply 2f component, it is likely that the electric current of the AC motor changes to an over current or large pulsation occurs in the torque of the AC motor to hinder a safe operation.
Patent Document 1 discloses that such a power supply 2f component included in the DC voltage is extracted and the width of a PWM pulse of the inverter circuit is adjusted to cancel the influence of the power supply 2f component.    Patent Document 1: Japanese Patent Application Laid-open No. S56-49693